🚀 go-pugleaf

In article <1992Oct2.195944.772@nntpd2.cxo.dec.com> kgibsonkgibson@cxcad%decwrl.dec.com (Ken Gibson) writes:
>
>  Can someone post an M68000 version of the assembly language context switch
>routine _ctxsw for Xinu?  
>
>Many Thanks


*-----------------------------------------------------------------------------
* ctxsw  --	actually perform context switch, saving and loading registers
*		This routine is executed in kernel mode.
*
*		Upon entry, d0-d7, a0-a6, the usp, the sr, and the pc are
*		saved.
*
*		Upon exit, all registers saved are restored, and the value
*		of the user stack pointer is copied into the user 
*		stack pointer.
*-----------------------------------------------------------------------------

	section	14

	xdef	.cnt_ctxsw

.cnt_ctxsw	dc.l	0

	section	9

	xdef	.ctxsw

.ctxsw:
	addq.l	#1,.cnt_ctxsw
	move.l	a0,-(sp)	 		; Save A0 onto old stack	
	move.l	8(sp),a0			; Move address of old area into A0 
	movem.l	d0-d7/a0-a7,(a0)	; Save all registers		
	move.l	(sp),32(a0)			; Put original A0 in old savearea	
	addq.l	#8,60(a0)			; Move SP beyond return address
								; 	as if a return has occured
	add.l	#64,a0				; Skip past registers d0-7,a0-7
	move.w	#0,(a0)+ 			; Pad SR savearea, since SR is a word
	move.w	sr,(a0)+			; Save SR in old savearea
	move.l	4(sp),(a0)+			; Save PC in old savearea


*Save image:d0,d1,d2,d3,d4,d5,d6,d7,a0,a1,a2,a3,a4,a5,a6,ssp,0x00, sr, pc
*            0  4  8 12 16 20 24 28 32 36 40 44 48 52 56  60  64   66  68

	move.l	12(sp),a0			; Move address of new area into A0
	movem.l	(a0),d0-d7/a0-a6	; Restore all regs (even A0) except SP
	move.l	12(sp),a0			; Move address of new area into A0 again
	move.l	60(a0),sp			; Put  SSP into kernel stack
	move.l	68(a0),-(sp)		; Move PC onto current stack	
	move.w	66(a0),sr			; Restore the status register
	move.l	32(a0),a0			; Restore A0 from new area
	rts							; since we pushed the pc onto the stack,
								;   we just pretend to return






---JR---


-- 


   /------------------------------------------------------------------\
  |  John Reed                           {ucsd,uunet}!pacdata!johnr    |
  |  Pacific Data Products               johnr@pacdata.com             |
  |                    ---------------------                           |
  |  George Herbert Walker Bush, with the letters re-arranged spells:  |
  |                                                                    |
  |                 Huge Berserk Rebel Warthog                         |
  |                                     -- From Cosmic Trigger II      |
   \------------------------------------------------------------------/